These “rules” are set by BIS and not PMC :)
The texture name should be simple ascii, containing only letters, digits and underscore (no letters with diacritics). Only one dot is allowed leading the extension.
Example of texture name: M151A1_fuelTank01_CO.tga
The source texture file format is PNG (preferred) or TGA (no compression, only 24b or 32b).
textureType is predefined suffix, that allows to choose proper compression and other transformation for the texture. The actual transformation is defined by TexConvert.cfg used by both Pal2PacE and TexView 2 tools).
_CO - color (diffuse map), sRGB color space
_CA - color with alpha (diffuse map with alpha), sRGB color space
_NO - normal map
_NS - normal map specular (with alpha)
_NOF - normal map faded (mipmaps fade the texture in distance, useful for terrain)
_NON - normal map with noise in alpha channel ( noise is used for vegetation LODs blending)
_NOHQ - normal map high quality
_NOVHQ - normal map high quality
_DT - detail texture, average color should be 0.5, texture has got fade out filter in mipmaps
_CDT - colored detail texture, average color should be 0.5 in all R G B channels, texture has got fade out filter in mipmaps
_SKY - sky texture
_MC - macro texture, sRGB color space
_AS - ambient shadow texture
_SM - specular map
_SMDI - optimized specular map for better bit depth
_LCO - layer color map, texture used for satellite and mask textures on the terrain
_MCO - multiply color map, texture used to multiply with color map (as cdt) without fade out filter, average color should be 0.5 in all R G B channels
Only some formats use sRGB Color Space, other use linear space.